Conference connection and control device for telephone subscriber lines



H. SHAW Filed March 5, 1965 I 3 w I INVENTOR.

WALTER H. SHAW BY MN 5M CONFERENCE CONNECTION AND CONTROL DEVICE FORTELEPHONE SUBSCRIBER LINES June 18, 1968 I I I I I I I l I 1 l l lATTORNEY.

United States Patent 3,389,224 CONFERENCE CONNECTlON AND CONTROL DE-VICE FOR TELEPHONE SUBSCRIBER LINES Walter H. Shaw, Miami, Fla.,assignor to Shaw Electronics Incorporated, a corporation of FloridaFiled Mar. 5, 1965, Ser. No. 437,443 4 Claims. (Cl. 179-1) ABSTRACT OFTHE DESCLOSURE The invention consists of a conference connection andcontrol device for telephone subscriber lines whereupon a controllingsubscriber having a plurality of subscriber lines terminating at his setmay interconnect these subscriber lines to form a conference circuit.The conference and control circuit consists of a pair of subscriberlines, that are terminated at the control subscribers set and undercontrol of line button keys at the set, connected in parallel across theprimary of a transformer and another pair of subscriber lines connectedin parallel across the secondary. Each subscriber line is connected intothe circuit and is under the control of a three position toggle switch.The switch has a talk, hold and disconnect" position. In the holdposition, an indicator lamp approximately equal in impedance to asubscriber set is switched into the conference circuit. The controlsubscriber brings the other subscribers into the conference circuitindividually and manually. The line button keys of the set connect thecontrol subscriber to the various outgoing lines and the three positiontoggle switches hold the subscriber lines connected while the controlsubscriber is dialing out on another line.

My invention relates to telephone conference control circuitry and isdirected particularly to a device for controlling conference connectionwith and among a plurality of remote telephone subscribers at asubscriber station having a plurality of telephone circuit subscriberlines.

The principal object of my invention is to provide a conference controldevice of the character above described that enables a subscriber at thecontrolling station to make successive outgoing cells to persons at aplurality of mutually'remote stations to bring them into conferenceconnection with him and 'with any or all of the other remote stations,selectively, and to selectively hold and disconnect each of the remotelines at will, whereby complete control of the telephone conferenceconnection with respect to calling, holding, interconnecting forconference and disconnecting each of the individual remote stationscalled is maintained at the controlling station.

A more particular object is to provide a conference control device ofthe above nature which enables the controlling subscriber to place theplurality of calls to be brought into conference in the normal mannerthrough local and/or toll lines of a telephone system over a like numberof individual subsciber lines at the controlling subscriber station,whereby each line can be controlled individually as to when it isbrought into and dropped out of the conference connection for mosteconomical use of toll line facilities of the telephone system.

Still another object is to provide a conference control device of theabove nature wherein the status of each of the remote stations calledinto conference is controlled by an individual toggle switch havingtalk, hold and release positions, each position of which is indicated ormonitored by a single supervisory lamp, which lamp, in addition, servesas a terminal line impedance when its associated subscriber line is athold position.

seam Patented June id, 1968 Yet another object is to provide aconference control device that is compact, simple to install andoperate, and dependable and durable in use.

Other objects, features and advantages of the invention will be apparentfrom the following description when read with reference to theaccompanying drawing, the single figure of which illustrates,schematically, the circuitry of a conference connection and controldevice embodying the invention.

Referring now in detail to the drawing, the broken line box indicated atlit encompasses the internal cincuitry, shown schematically, of mydevice, the same having a plurality (four in the embodiment illustrated)of ring and tip line pairs K1, T1; R2, T2; R3, T3 and R4, T4,respectively, externally connected, correspondingly, to the ring and tipleads of telephone subscriber lines L1, L2, L3 and L4 available forconference connection at the controlling subscriber station. A telephonesubscriber :handset lll associated with individual subscriber lines L1,L2, L3 and L4 and connectable individually and selectively thereto underthe control of line button keys LE1, LE2, LE3 and LE4 as in an ordinarymultiple-line subscriber service installation is used to make theoutgoing calls to and for conferring with the remote stations in themanner hereinafter described. Toggle switches 12, 13, i4 and 15 controlthe individual lines L1, L2, L3 and L4, with respect to their talk, holdand release status, as is hereinbelow described.

Toggle switch 12 comprises a normally open, singlepole, single-throwswitch 16 having fixed contact arm 16a and movable contact arm lob; asingle-pole, doublethrow switch 17 comprising fixed contact arms 17a and17b and movable contact arm 17c normally in contact with fixed contactarm 17!); and a normally closed singlepole, single-throw switch 18comprising fixed contact arm 18a and movable contact arm 13!). Fixedswitch contact arm 16a is connected, as by conductor 19, to fixedcontact arm 17a. Movable contact arm 16b is connected, as by conductor2%, to movable contact arm l8!) and thence, as by conductor 21, to oneterminal of a supervisory lamp 12a associated with switch 12. Theremaining terminal of the supervisory lamp 12a is connected, as throughlead 22, to line tip terminal Tl. The movable contact arm 17c associatedwith switch 17 is connected, as through lead 23, to line ring terminalR1. The fixed contact arm 17b associated with switch 17 is connected, asby conductor 24, to the positive terminal of a diode rectifier 25, thenegative terminal of which is connected, as by conductor 26, to oneterminal of a winding 2'7 of a two-winding, one-to-one ratio repeattransformer 28. The other terminal of the winding 27 is connnected, asby conductor 29, to thefixed contact arm 18a associated with switch 1%.

Toggle switch 13 is similar to switch 12 associated with line L1 andcomprises a normally open single-pole, singlethrow switch 39 havingfixed contact arm 3% and movable contact arm 39!); a single-pole,double-throw switch 31 comprising fixed contact arms 31a and 31b, andmovable contact arm 31c normally in contact with fixed contact arm 31b;and normally closed single-pole, single-throw switch 32 comprising fixedcontact arm 32a and movable contact arm 32b. Fxed contact arm 39a isconnected to fixed contact arm 33in as by conductor 33. Movable contactarm Eitlb is connected to fixed contact arm 32a as by conductor 34.Fixed contact arm 31b is connected through conductor 35 to the positiveterminal of a diode rectifier at) the negative terminal of which isconnected, as by conductor 41, to conductor 26 leading to transformerwinding 28. Movable contact arm 310 is connected, as by conductor 39, toline ring terminal R2. Movable contact arm 32b is connected, as byconductor 37, to one terminal of a supervisory lamp 13a, the other '2 onterminal of which connects to tip terminal through conductor The threeposition tcgg swi cal with switches l2 and i3 and are connected byidentical circuitry, including diode rectifiers M and 45', to the otherwinding 47 of repeat transformer in. to provide conference connection tothe two a 'onal subscriber lines L3 and L4 through ring and tip t nunalpairs K3, T3 and R4, T l.

In the use of my conference connec ion and control device, telephone 11will be employed in ordinary fashion to make a call to the first remoteto be called into conference, through line Ll, for example, asillustrated by the brokendine representation of connection with sai lineeffected by pushing down the corresponding line button key LE1 of saidtelephone. Tl" witch 12, being at talk position, as illustrated by the l:e re entation oi its associated switch arms, establishes a circuit fromthe tip lead of line Ll throu l conductor la'up 22a, conductor 21,closed switch lea, 13b, a d conductor 21 to one ll of the winding 27comp ing repeat transformer 28, thence, from the other terminal of saidtra ormer, conductor 26 to the negative terminal of ne diode 25, andthence, from the positive terminal of said diode, through conductor 234,closed switch 17b, 17c, and conductor 23 to ring lead of line Ll. Sincepositive polarity appears at the ring terminal and negative at the tipterminal in a normal telephone line before its connection in a talkingcircuit, the diode at this point oloclts the flow of line currentthrough the repeat tra slormer 27 in the just described circuit.Iowever, the ca led person, in picking up the handset at the remotecalled station, will eilect polarity reversal in the now estab" d firsttalking circuit in accordance with standard telephone circuitryoperation, so that a direct current path is established through thediode 25, the repeat transformer 27, and the supervisory lamp 12:1. Thelamp 12a will thus light. being energized by the direct current in thetalking circuit line. ireferably, the toggle switch 12 is of the typeincorporah ing the indicator lamp 12a and having colored lensescontrolled by switch lever position to indicate switch position byluminous color code. Thus the lamp 12a will not only light, but willshine through a lens of a particular color, green for example,indicating that a talking circuit has been established to the firstremote station called into conference. The switch 12 will then be placedin the hold position, as illustrated by the dotted line representationof its associated switch arms and to place the supervisor-y lamp 12adirectly across the line Ll. from tip terminal Til, through conductor 22to one terminal of said lamp, thence, from the other terminal of saidlamp, through conductor Zll. closed switch 38a, 18b, conductor 20, nowclosed switch 16a, ib, conductor 19, now closed switch 17:1, 170, andconductor to ring terminal P The lamp 12 thus serves as a terminalimpedance for line to maintain connection with the first called remotestation. In the hold position of the switch, the lamp could shinethrough a red lens, for example, controlled by switch position asdescribed above.

The telephone 11 will then be connected to line L2, by pressing down keybutton LBZ so that an outgoing call can be made in the usual way to thesecond remote station to be called into conference. As described abovein connection with circuit associated with switch l2, in making thesecond outgoing call the switch 15 will be placed in talk position, asillustrated by the full-line position of the associated switch arms, thediode preventing fiow of current until the second person called intoconference picks up his handset, at which t me line polarity reverses toplace the winding 27 of the repeat transformer 28 in connection acrossthe line L2 in series with the supervisory lamp Clan. The lamp will thusbe ener ized and shine thr a green lens, for example, 1mg that theswitch is in talk position. At this point, the switch 12 associated withline Llt can be placed in talk 16S and ii; are identiills positionagain, assuming it had been placed in hold position, enabling the firsttwo remote parties brought into conference to ta k together while thecontrolling subscriber makes additional outgoing calls through his linesL3 L4. As soon as a talking circuit is established for each new r otesubscriber brought into conference, he can t a with those alreadybrought into conference provided their associated switches 12, 13, etc.at the controlling station are in talk position. While only four talkingircuits for four lines are shown, additional windings on he repeattransformer 23 could be provided for adding icentical line controlcircuitry, preferably in line pairs for each additional winding, asillustrated. The controlling subscriber will be able to tall; inconference no matter in which line he happens to be connected, providedits associated switch is in talk position. The controlling subscrisercan disconnect any established talking circuit sim lv by placing theassoci ted switch in disconnect or release position, the positionrepresented by the open dash-dot line position of switch arm 13!)associated with toggle switch 12, for example. In this switch position,the above-described talking circuit through normally closed switch 18 torepeat coil is opened, disconnecting associ ed line L1 from conferenceconnection. The controlling su riber can still tallz, privately, ifdesired, with the remote station connected to line Lil provided histelephone set is connected across the line, as illustrated in thedrawing. As soon as the controlling subscriber replaces the handset, orswitches to one of the other remote station lines, line Ll will bedisconnected. Thus it will be apparent that the controlling subscriberhas complete con trol as to who is brought into conference, which ofthose brought in are in talking or hold status at any particular time,which are conferred with privately at any time, and which are releasedor disconnected at any time. It will also be understood that the numberof remote stations rought into conference is limited only by the numberof individual subscriber lines available at the controlling station.

While I have illustrated and described herein only one form in which myinvention can conveniently be embodied in practice, it is to beunderstood that this form is presented by way of example only, and notin a limiting sense. My invention, in brief, comprises all themodifications and embodiments coming within the scope and spirit of thefollowing claims.

What I claim as new and desire to secure by Letters l-atent is:

l. A conference conncctio and control device for telephone subsc'iberines compi 1;, in combination, a repeat coil, a plurality of tip andring terminal pairs for connection, one pair each, to a like pluralityof subscriber lines at the controlling subscriber station, an electricalcircuit interconnecting each of said tip and ring terminal pairs withsaid repeat coil, for transmitting voice frequency elec trical cu rentstherebetwu a rectifier in each of said circuits series-connected '\..Ll1said repeat coil, 2. supervisory lamp in each of said circuits,series-connected with its associated tip terminal, a three positionswitch means in each of said circuits and having tali', hold and releasepositions, said switch when in said talk position being operative toconnect its associated tip and ring terminal pair across said repeatcoil through its associated supervisory lamp and rectifier, said switchwhen in said hold position being operative to connect its associatedlamp directly across its associated tip and ring terminals, and saidswitch when in said release position being operative to open-circuit itsassociated circuit at its supervisory lamp.

2. A conference connccton and control device for telephone subscriberlines as defined in claim 1 wherein the polarity of connection of saidrectifier is such as to block the llow of current to said repeat coiluntil line polarity of a subscriber line connected to the associated tipand ring terminal pair is reversed by the answering of a remotesubscriber station called over said subscriber line.

3. A conference connection and control device for telephone subscriberlines as defined in claim 2 wherein the electrical characteristics ofsaid supervisory lamp are such as to be energized to incandescence bystandard subscriber line potential and at the same time serve as aterminal impedance for holding the telephone line when shunted directlythereacross.

repeat coil comprises a plurality of separate windings, two of saidcircuit means being connected to one of said windings.

References Cited UNITED STATES PATENTS 3,331,924 7/1967 Reaves l79-1KATHLEEN H. CLAFFY, Primary Examiner.

4. A conference connection and control device for tele- 10 A. H. GESS,Assistant Examiner.

phone subscriber lines as defined in claim 2 wherein said

